1. Field of the Invention
The present invention relates to a tunneling transistor that is applicable to nonvolatile memory.
2. Related Art
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), in which a thin oxide insulating film is deposited on a semiconductor substrate and a gate electrode is provided on the insulating film, operates as a transistor based on the principle that a current flowing through a semiconductor channel between a source and a drain located beneath the gate electrode is modulated by a voltage (xe2x80x9cgate voltagexe2x80x9d) applied to the gate electrode. However, as the length of the channel gets closer to 10 nm due to miniaturization of the transistor, a problem known as xe2x80x9cshort-channel effectsxe2x80x9d arises, which makes it impossible to control the amount of current passing through the channel by the gate voltage. To overcome this problem while reducing the channel length, a tunneling transistor has been devised which, having formed a channel from a material such as an insulator that provides a tunnel barrier, controls the amount of current flowing through the channel by varying the barrier potential of the insulator (see E.S. Snow et al. Applied Physics Letters, vol. 72, pp. 3071-3073 (1998)).
However, such a tunneling transistor does not possess a memory function, and therefore is not applicable for miniaturization of semiconductor integrated circuits having memory circuits.
The present invention aims to provide an effective means that fosters miniaturization of a semiconductor integrated circuit having nonvolatile memory.
This object can be achieved by a tunneling transistor having a source, a drain, and a gate, including: a tunnel barrier layer which forms a tunnel barrier between the source and the drain; and a ferroelectric layer which exhibits spontaneous polarization, wherein when the ferroelectric layer is polarized in a predetermined direction, the polarization induces formation of a depletion region within a region of the source that is adjacent to the tunnel barrier layer.
With this construction, storing of data is performed by exploiting the phenomenon in which a current tunneling through the tunnel barrier layer provided as the channel between the source and the drain varies due to spontaneous polarization of the ferroelectric layer. Since the tunnel barrier layer is generally made of a material such as an ultrathin insulator, the length of the channel can be reduced, which benefits miniaturization of a semiconductor integrated circuit having nonvolatile memory.